Embolic filter with a distal loop

ABSTRACT

The invention provides a device for filtering emboli from blood flowing through a lumen defined by the walls of a vessel in a patient&#39;s body, comprising a filter element and a self-expanding radial element associated with the filter element. The filter element is expandable from a collapsed configuration when the filter element is restrained to an expanded configuration when the filter element is unrestrained. The filter element comprises a self-expanding material having pores. The filter element has proximal and distal portions and a central portion, and has a shape in the expanded configuration which defines a cavity having a proximal facing opening. The self-expanding radial element is distal of the filter element, and the self-expanding radial element is adapted to maintain the filter element centered in the lumen.

This application is a continuation of U.S. patent application Ser. No.11/374,943 by Kusleika et al., filed on Mar. 14, 2006, which is acontinuation of U.S. patent application Ser. No. 10/354,831 by Kusleikaet al., filed on Jan. 30, 2003, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to devices used in a blood vessel or other lumenin a patient's body. In particular, the present invention relates todevices for capturing emboli and particulate in a lumen.

BACKGROUND OF THE INVENTION

During vascular surgery or endovascular treatment of vessels includingthrombectomy, atherectomy, balloon angioplasty, and/or stent deployment,debris such as plaque and blood clots can move from the treatment sitethrough a vein or artery and compromise the flow of blood at a locationremoved from the treatment site. In particular, various protectionsystems have been developed to prevent such debris from embolizing inthe vessel. Distal protection devices include filters and occlusivedevices (e.g., balloons) placed distally of the treatment site. Proximalprotection devices include filters and occlusive devices placedproximally of the treatment site. In the case of filters, emboli collectwithin or on the filter. The filter with captured emboli is typicallycollapsed into a recovery catheter and the catheter withdrawn from thepatient's body.

In prior art filters it has been found that incorrect radial position ofthe filter within a body conduit can compromise the performance of thefilter. Specifically, if a portion of the filter abuts a vessel wall,then the area of the filter available for performing the filteringfunction is reduced. Further, radial motion of an elongate member cancause the filter to lose wall apposition and thereby defeat the intendedembolic capture function of the filter.

Most filters are mounted onto elongate support members, and the filtersare comparatively flexible as compared to the elongate support membersto which they are mounted. Radial motion of the elongate support memberis often a consequence of back and forth axial motion of the elongatesupport member in tortuous body conduits. Radial motion of the elongatesupport member can compress the filter, causing it to lose apposition tothe conduit wall and thereby defeat the intended embolic capturefunction. Control of elongate member radial position by use of proximalloops is discussed in U.S. Ser. No. 09/628,212, filed Jul. 28, 2000,entitled “Improved Distal Protection Device” and U.S. Ser. No.10/093,572, filed Mar. 8, 2002, entitled “Distal Protection DevicesHaving Controllable Wire Motion,” the contents of each of which arehereby incorporated by reference herein. Radial motion of the elongatesupport member can also press the filter against a conduit and reducethe area available for filtering emboli.

A need in the art remains for an embolic protection filter in which anelongate support member does not cause the filter to have excessivecontact with a body conduit, thereby decreasing the filter areaavailable for performing the filtering function.

SUMMARY OF THE INVENTION

The invention provides an embolic protection filter in which an elongatesupport member does not cause the filter to have excessive contact witha body conduit, thereby decreasing the filter area available forperforming the filtering function. The invention also provides anembolic protection filter in which radial wire motion does notcompromise filter wall apposition.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view and FIG. 1B is a cross sectional view of a priorart filter deployed in a body conduit.

FIG. 2A is a side view and FIG. 2B is a cross sectional view of anembodiment of the invention showing a distal loop.

FIG. 3 is a side view of an embodiment of the invention showing a distalloop and a tether.

FIG. 4 is a side view of an alternate embodiment of a filter of thisinvention.

FIG. 5 is a side view of a no loop filter.

FIG. 6 is a side view of an alternate embodiment of a no loop filter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “distal” and “proximal” as used herein refer to the relativeposition of the elongate support member, catheters, and filter in alumen. Thus, “proximal” refers to a location upstream from the “distal”position. That is, the flow of a body fluid, such as blood, moves fromthe proximal to the distal portions of the device.

The invention encompasses the use of any filtration device to bedeployed in a lumen or vessel of a patient. Although the examples relategenerally to filter protection devices deployed distal to a treatmentsite, the device can also be deployed proximal to a treatment site inconnection with interrupting or reversing flow through the vessel. Inthe case of a proximally deployed device, it will be advantageous toconstruct the device on a hollow elongate member so as to preserveaccess to the treatment site through the hollow member.

In a preferred embodiment, the distal protection system comprises acatheter which is loaded with an elongate support member or guidewireabout which is disposed a distal protection filter. The elongate supportmember is structurally similar to a traditional guidewire in somerespects. However, it is not used as a means of navigating the patient'svascular system and, therefore, does not need to be provided with all ofthe features of flexibility and steerability as does a traditionalguidewire. With these differences in mind, the terms elongate supportmember and guidewire may be used interchangeably herein. A floppy tip(described further below) may be at the distal end of the elongatesupport member or guidewire. Typically, the filter is introduced into ablood vessel through an introducing catheter. Methods of introducingguidewires and catheters and the methods for the removal of such devicesfrom vessels are well known in the art of endovascular procedures. In atypical procedure using the device of this invention, the elongatesupport member and filter are loaded into an introducing sheath orcatheter and moved into the vessel and through the catheter to thetreatment site. Typically, this is done by advancing a first, orintroduction guidewire, through the vessel to the region of interest. Acatheter is advanced over the guidewire to the region of interest, andthe guidewire removed. Then the filter or other functional devicecarried by the elongate support member is advanced down a cathetersheath to the region of interest but within the catheter. The cathetersheath is withdrawn to deploy (expand) the filter at the region ofinterest. Alternatively, the filter is pre loaded into a catheter andheld in place by an outer sheath of the catheter and they are togetheradvanced through the vessel to the region of interest without using aninitial guidewire. In this embodiment the catheter/filter combinationwill be used to navigate through the vessel to the region of interest.Then the catheter is withdrawn to deploy the filter. In a secondalternative, an introduction guidewire is advanced to the region ofinterest, and the filter (contained in a catheter) is advanced over theguidewire to the region of interest, at which point the catheter isremoved leaving the deployed filter near the region of interest on theguidewire. In this embodiment the filter is not comprised of an elongatesupport member as previously defined, and the guidewire and/or filtermay be configured to preserve a spatial relationship between theguidewire and the filter. For example, the guidewire may be configuredto prevent the filter from advancing beyond the distal end of theguidewire.

In other embodiments of the invention, no catheter is required forfilter delivery. For example, the filter may be stretched axially so asto reduce its diameter to a size suitable for navigation through avessel and across a treatment site.

Typical dimensions of a filter used in the devices of this inventionrange from 2 mm to 90 mm in length, and from about 0.5 mm to 2 mm indiameter 5 before deployment, and from about 2 mm to 30 mm in diameterafter deployment. A typical guidewire is about 0.2 to 1.0 mm in diameterand ranges from 50 cm 320 cm in length.

The components of the distal protection system are made frombiocompatible materials. Materials also may be surface treated toproduce biocompatibility. The elongate support member may be formed ofany material of suitable dimension, and preferably comprises metal wire.

Suitable materials include stainless steel, titanium and its alloys,cobalt-chromium-nickel-molybdenum-iron alloy (commercially availableunder the trade designation Elgiloy™), carbon fiber and its composites,and engineered polymers such as liquid crystal polymers,polyetheretherketone (PEEK), polyimide, polyester, and the like. A shapememory or superelastic metal such as nitinol is also suitable. Theelongate support member may be solid or may be hollow over some or allof its length.

The material used to make the filter or filter support structure ispreferably self-expanding. Suitable materials include metals such asstainless steel, titanium and its alloys,cobalt-chromium-nickel-molybdenum-iron alloy (commercially availableunder the trade designation Elgiloy™), carbon fiber and its composites,and engineered polymers such as liquid crystal polymers,polyetheretherketone (PEEK), polyimide, polyester, silk, and the like. Ashape memory or superelastic 25 metal is particularly suitable for thoseapplications when it is desired for an element, such as a filter, toassume a pre-determined three-dimensional shape or for a guidewire tomaintain a pre-determined curvature. A shape memory or superelasticmetal comprising nickel and titanium known as “nitinol” is commerciallyavailable in various dimensions and is suitable for use as both aguidewire and a filter. For example, nitinol tubular braid can be heatset into a desired shape, compressed for delivery to a site, and thenreleased to resume the heat-set shape.

The filter element has a body defining an interior cavity. The filterbody has a plurality of openings or pores such that, when the filterelement is in its deployed configuration within the vessel lumen, fluidflows through the filter element and particles of the desired size arecaptured inside the interior cavity of the filter element.

The filter may comprise any material that is suitably flexible andresilient, such as a mesh, i.e., a material having openings or pores.The filter may comprise braided, knitted, woven, or non-woven fabricsthat are capable of filtering particles, preferably having pore sizesfrom 30 to 500 microns. Woven or nonwoven fabrics may additionally betreated to fuse some or all of the fiber intersections. The fabric maybe spun or electrospun. Suitable materials include those formed fromsheets, films, or sponges, polymeric or metallic, with holes formed bymechanical means such as laser drilling and punching, or by chemicalmeans such as selective dissolution of one or more components. Forexample, a suitable filter material is braided tubular fabric comprisingsuperelastic nitinol metal. Mesh fabric of nitinol material can beheat-set to a desired shape in its expanded configuration.

The material comprising the filter is preferably at least partiallyradiopaque. This material can be made radiopaque by plating, or by usingcore wires, tracer wires, or fillers that have good X-ray absorptioncharacteristics compared to the human body. Radiopaque filters aredescribed in U.S. patent application Ser. No. 10/165,803, filed Jun. 7,2002, entitled “Radiopaque Distal Embolic Protection Device,” thecontents of which are hereby incorporated by reference herein.

The embodiments of this invention, described in detail below inconnection with the figures, are suitable for use with various distalprotection systems that are known in the art. The filter may have awindsock type shape. The construction, deployment and retrieval of afilter having this shape is described, for example, in U.S. Pat. No.6,325,815 B1 (Kusleika et al.), the contents of which are herebyincorporated by reference herein.

The filter may also be a cup-shaped or basket-shaped device which formsa proximally facing opening when expanded. The construction, deployment,and retrieval of such a filter is described in WO 96/01591 (Mazzocchi etal.). This cup-shaped device may generally resemble an umbrella or aparachute, having a dome-like structure curving radially outwardly fromthe guidewire or elongate support member. Other shapes may be equallysuitable in performing a filtering function, such as a conical shape, ora relatively flat disc shape. It will be appreciated that the shape ofthese filtration devices shown in various embodiments are merelyillustrative and are not meant to limit the scope of the invention.

Regardless of the shape of the filter, the filter preferably is deployedusing an elongate support member. This can be done in various ways, andone or both of the proximal and distal ends of the filter may be affixedto the elongate support member (by a fixed element) or may be slidablydisposed about the elongate support member (by one or more slidingelements).

One type of sliding element comprises inner and outer annular rings. Thefirst ring fits within the second ring. The inner diameter of the firstring is larger than the diameter of the elongate support member so thatthe sliding element can slide over the elongate support member. Thesliding element can be affixed to the filter fabric by placing thefabric between the first and second rings. However, this is not meant tobe limiting, and the filter fabric can also be affixed to the slidingelement by adhesive, solder, crimping, or other means known in the art.The sliding element may comprise any stiff material such as metal orpolymer and preferably the slider is radiopaque. Suitable materialsinclude stainless steel, titanium, platinum, platinum/iridium alloy,gold alloy, polyimide, polyester, polyetheretherketone (PEEK), and thelike. Movement of a sliding element with respect to the elongate supportmember can be facilitated by coating one or both of the inside of thesliding element and the outside of the elongate support member with afriction-reducing coating, such as polytetrafluoroethylene or alubricious hydrophilic coating.

Fixed elements include annular rings. Also included within this meaningis an element that is crimped, adhered, soldered, or otherwise fasteneddirectly to the elongate support member. Also, the filter fabric may beattached directly to the elongate support member. In any event, thesliding and fixed elements (or any attachment point) typically compriseradiopaque material to assist in the placement of the filter. Inaddition, one or more radiopaque markers may be positioned at variouslocations on the protection device. These radiopaque markers or markerbands comprise a material that will be visible to X-rays and they assistin positioning the device.

Some distal protection filters include a floppy tip at a distal portionof the guidewire or elongate support element. The floppy tip provides anatraumatic and radiopaque terminus for the device. An atraumatic tipprevents vessel injury during initial placement or subsequentadvancement of the device. A radiopaque tip helps the physician verifysuitable tip placement during fluoroscopy. The floppy tip preferablycomprises a springy or resilient material, such as a metal (e.g.,stainless steel, iron alloys such as Elgiloy™, platinum, gold, tungsten,and shape memory or superelastic metal such as nitinol) or polymer(e.g., polyetheretherketone (PEEK), polyimide, polyester,polytetrafluoroethylene (PTFE), and the like). Springy materials aredesirable because they tend to retain their shape. The physician willinitially shape the tip, typically with a slight curve, and then as thedevice is advanced through the body the tip will be deflected as itencounters obstacles. It is desirable, after the inevitable deflectionsduring insertion, that the tip restore itself to the pre-set shape.Polymeric materials additionally may be reinforced with metals or otherfillers. The tip may be a monofilament or multifilament (such as acable). The floppy tip may be tapered or have a uniform diameter overits length. The floppy tip may comprise a tube, or could have circular,flat, or other cross-sections. It may be coiled. The tip may compriseone or more elements (for example, parallel independent structures). Thetip may be polymer-coated or otherwise treated to make the surfaceslippery. The floppy tip can be any desired length.

The filter comprises biocompatible materials such as metals andpolymeric materials. Materials such as metals and polymeric materialscan be treated to impart biocompatibility by various surface treatments,as known in the art. When wire is used, the wire is selected on thebasis of the characteristic desired, i.e., stiffness or flexibility, andthe properties can depend upon both the diameter of the wire and itscross-sectional shape. The size, thickness, and composition of elasticmaterials are selected for their ability to perform as desired as wellas their biocompatibility. It is to be understood that these designelements are known to one of skill in the art.

Filters are typically constructed as described in U.S. Pat. No.6,325,815 B1. See column 3, line 63, to column 4, line 16; and column 4,line 48, to column 5, line 36. The filter body typically comprises alength of a braided tubular fabric, preferably made of nitinol. Thefilter body is typically made by placing a braided tubular fabric incontact with a molding surface of a molding element which defines theshape of the desired filter body. By heat treating the braided tubularfabric in contact with the molding surface of the molding element, onecan create a filter body having virtually any desired shape.

Braiding is a process for producing a tubular interwoven structure fromindividual strands. Braids are typically produced in continuous lengthson commercially available braiding machines. Some commercial productsproduced on braiding machines include rope, shoelaces, and reinforcingjackets for electrical cable. Medical products produced by braidinginclude stents, vascular grafts, and catheter reinforcing layers.

In a typical braiding process for making a 72 stranded braid, lengths ofstrands, such as wire, are wound onto bobbins. In this example 72bobbins are wound with wire. Each bobbin is loaded into the carrier of a72 carrier braiding machine. Typically braiding machines for medical usehave from 16 to 144 carriers or more. Each wire is led through atensioning mechanism in the carrier and all wire strands are gathered ata common central elevated position along the (typically vertical) axisof the braiding machine, where they are fastened to a take-up mechanism.The take-up mechanism may be a long mandrel arranged along the axis ofthe braiding machine and onto which the braid is formed during thebraiding process. Once so configured, the carriers are rotated relativeto the axis of the braiding machine. The carriers are rotated in aserpentine path, half of them moving clockwise and the other half movingcounterclockwise, so as to interweave the strands in a programmedpattern. While the carriers are rotating, the take-up mechanism advancesthe woven braid in a direction away from the carriers. The combinationof these motions produces a helix of strands twisting in a clockwisedirection along the mandrel, interwoven with a helix of strands twistingin a counterclockwise direction along the mandrel. In this mannercontinuous lengths of braid are produced with an inside diameter of thebraid equal to the outside diameter of the braiding mandrel. Theindividual braid strands, while still on the mandrel, can be twistedtogether after the length of the mandrel has been braided. If desired,after removing the mandrel from the braiding machine, the strands can beheat-treated. In the case of nitinol strands, heat treatment on themandrel at about 525° C. for 10 minutes or so can cause thenitinol-braided fabric to remember the shape and size of the mandrelwhen the nitinol is at rest.

The average pore sizes of filters of the invention preferably range from30 to 300 microns. In another preferred embodiment, the average poresizes range from 30 to 150 microns. A pore size of about 120 microns ispreferred for devices intended to be used in connection with coronaryprocedures and a pore size of about 50 microns is preferred for devicesintended to be used in connection with carotid or intracranialprocedures. The variation in pore size within the filter should beminimized. In preferred embodiments of the invention, the standarddeviation of the pore size is less than 20 percent of the average poresize. In other preferred embodiments, the standard deviation of the poresize is less than 15, 10, 5, or 2 percent of the average pore size.

The percent open area of the filters of the invention is preferablygreater than 50 percent. In other preferred embodiments, the percentopen area is greater than 60, 70, or 80 percent. A standard formula isused to calculate the percent open area of a given design. The percentopen area is calculated by dividing the total pore area by the totalfilter area (including the pore area). The filters of the inventionpreferably are made of a material having a tensile strength of greaterthan 70,000 psi (7031 kg/cm²), more preferably greater than 150,000 psi(14,062 kg/cm²), and more preferably greater than 200,000 psi 15 (17,578kg/cm²). Cast polymer films have a maximum tensile strength of about10,000 psi (703 kg/cm²); oriented polymer films have a tensile strengthas high as 50,000 psi (3516 kg/cm²), and metal filters typically containwires having a tensile strength of from 70,000 to 300,000 psi (7031kg/cm² to 21,093 kg/cm²).

The various embodiments of the invention will now be described inconnection with the drawing figures. It should be understood that forpurposes of better describing the invention, the drawings have not beenmade to scale. Further, some of the figures include enlarged ordistorted portions for the purpose of showing features that would nototherwise be apparent. The material comprising the filter (e.g., mesh orfabric with pores, as described above) is omitted in the figures forsimplicity.

It is to be understood that the following embodiments are useful for anyshape or type of filter. For example, these embodiments are useful forany filter deliverable by any manner to a desired position in a bodylumen where control of the desired characteristics of the filter as setforth above is desired. In particular, the invention includes bothproximal and distal filters.

FIG. 1A illustrates a prior art distal protection system in whichwindsock-shaped filter 10 is attached to elongate support member 15 viadistal sliding element 18. For clarity, the mesh of the filter is notdrawn in the figure. At the proximal end of the filter, proximal slidingelement 16 is slidably disposed about the elongate support member andattached to filter 10. Stop 12 is provided on the elongate supportmember in order to limit the relative motion of the filter along thesupport member. Support member 15 terminates distally at floppy tip 15b.

When deployed in a vessel V, filter 10 has wall apposition regions 11 atthe proximal end of the filter and along the vessel wall. FIG. 1B showsfilter 10 and wall apposition regions 11 in cross section. Fluid flowcannot pass through filter 10 in wall apposition regions 11 becausethere is no space between the filter and the vessel in this region. Inthe case of a braided structure, flow cannot pass through distal portionof mesh 17 because the pores are generally very small. Most flow isconfined to passing through the central portion 13 of filter 10.

Distal Loop Filters

FIG. 2A is a side view and FIG. 2B is a cross sectional view of anembodiment of the present invention. Windsock-shaped filter 20 isattached to elongate support member 25 via distal sliding element 28.For clarity, the mesh of the filter is not drawn in the figure. At theproximal end of the filter, proximal sliding element 26 is slidablydisposed about the elongate support member and attached to filter 20.Stop 22 is provided on the elongate support member in order 25 to limitthe relative motion of the filter along the support member. Stop 22 maybe a wire coil or a hypotube, polymer or metal, solid, or cut to improveits flexibility. Stops and the use of stops are described in U.S. Ser.No. 10/060,271, filed Jan. 30, 2002, entitled “Slidable VascularFilter,” the contents of which are hereby incorporated by referenceherein. Support member 25 terminates distally at floppy tip 25 b. Distalloop 24 attaches to distal sliding element 28 and contacts vessel wall.Distal loop 24 may be made of elastic material such as metal or polymerand biased to expand when unconstrained. Suitable materials includenitinol, stainless steel, ELGILOY™, polyimide, PEEK, liquid crystalpolymer, polyester, and the like. If made of nitinol, the distal loopcan be heat set to the desired expanded shape for example by heating to525° C. for about two minutes. When deployed in a vessel V, filter 20has wall apposition regions 21 at the proximal end of the filter but notalong the vessel wall distal of the proximal end. FIG. 2B shows filter20 in cross section, where it is apparent that wall apposition regionsare not present as they are in FIG. 1B. In the case of a braidedstructure, flow cannot pass through distal portion of mesh 27 becausethe pores are generally very small. Most flow is confined to passingthrough the central portion 23 of filter 20, and this central portion 23of filter 20 is enlarged compared to prior art filters due to the effectof distal loop 24.

In FIG. 2, due to the effects of the distal loop, the wall appositionregion of the filter is reduced compared to prior art filters. However,the radial motion of the elongate support member 25 wire can compromisethe necessary wall apposition of the proximal end of filter.

FIG. 3 illustrates a windsock-shaped filter 30 attached to elongatesupport member 35 via distal sliding element 38. For clarity, the meshof the filter is not drawn in the figure. At the proximal end of thefilter, proximal sliding element 36 is slidably disposed about theelongate support member and attached via tether 36 a to point 36 b onthe filter 30. Stop 32 is provided on the elongate support member inorder to limit the relative motion of the filter along the supportmember. Stop 32 may be a wire coil or a hypotube, polymer or metal,solid, or cut to improve its flexibility. Support member 35 terminatesdistally at floppy tip 35 b. Distal loop 34 attaches to distal slidingelement 38 and contacts the vessel wall. Distal loop 34 can attach tothe proximal end, distal end, or at any point along distal slidingelement 38, and is configured so as to collapse into a catheter of lowprofile by incorporating hinges, zones of preferential bending, and thelike.

Tether 36 a reduces the influence of radial wire motion on the filtermouth. Tether 36 a may be made of any strong biocompatible flexiblestrand. Suitable materials include metal, polymer, monofilament,stranded, or cabled. For example, 0.004 inch (0.10 mm) diameter nitinolstranded wire made of 7 strands can be used. More preferably, 0.004 inch(0.10 mm) diameter 49 stranded nitinol cable can be used. Stranded wiregenerally has more flexibility than monofilament wire of the sameoverall diameter, and cabled wire generally has more flexibility thanstranded wire of the same overall diameter. Other suitable materialsinclude KEVLAR™ fiber, DACRON™ fiber, and other textile fibers.Stainless steel wires, particularly in stranded or cabled form, may bepreferred in some embodiments due to their high strength. Further, it isdesirable to coat the tethers with thrombosis reducing materials such asheparin to reduce clot formation on the tether.

By positioning elongate support member 35 such that there is slack intether 36 a, the elongate support member can move laterally within thefilter without compromising filter wall apposition. Tethers are moreeffective at accommodating lateral elongate member motion as compared tothe struts commonly used in prior art designs. It is also expected thatproximal sliding element 36 will slide to relieve tether tension in theevent of lateral or radial elongate member motion, thereby preventingloss of filter apposition to a vessel wall. Struts, common in prior artdesigns, do not afford this degree of freedom for accommodating elongatemember motion. In addition, by locating elongate member 35 within filter30, lateral motion of the elongate member will tend to press filter 30against the vessel wall because the filter wall is between the vesseland the elongate member. Further, good wall apposition of a given filtersize is expected over a range of vessel diameters because there is nostiff hoop at the opening of filter 30, rather, the filter mesh isgathered at connection 36 b. In contrast, many prior art designs have astiff hoop at the proximal end of the filter and such designs havedifficulty accommodating a range of vessel diameters due to thedifficulty in collapsing the stiff hoop while maintaining close contactwith the vessel wall.

This device can be deployed and used as follows. The proximal end ofelongate member 35 is inserted into the distal end of catheter C (backloaded into catheter). Elongate member 35 is withdrawn proximallythrough catheter C causing stop 32 to contact slider 36, causing tensionto be applied to tether 36 a and resulting in filter 30 being drawn intocatheter C due to attachment of tether 36 a to filter 30 at point 36 b.Further proximal motion of the elongate member through catheter C drawsthe rest of filter 30, distal loop 34, and optionally floppy tip 35 binto catheter. The catheter with filter assembly therein is advanced toa region of interest and deployed nearby, generally distal of the regionof treatment in the embodiment shown in FIG. 3. Filter deployment isaccomplished by advancing filter 30 distally relative to catheter C. Ina preferred embodiment, filter 30 in catheter C is positioned distal toa treatment site, and catheter C is withdrawn proximally. Filter 30 willremain inside catheter C due to friction of filter against catheterwalls until distal sliding element 38 contacts stop 32. Catheter C willthen slide relative to filter 30, with reduced friction due to thetendency of filter 30 to elongate and reduce in diameter due to actionof stop 32 on distal sliding element 38. As catheter C is withdrawnproximally relative to filter 30, first distal loop 34, then filter 30will exit the catheter and expand to contact the vessel wall. Catheter Ccan then be withdrawn proximally and removed from the patient. At thispoint, treatment and diagnostic catheters can be introduced overelongate member 35. Excessive motion of filter 30 against the wall ofvessel V during catheter exchanges is prevented because sliders 36, 38allow axial and rotational motion between elongate member 35 and filter30. During treatment or diagnosis, emboli may be released from thetreated or diagnosed site and may be collected in the filter.

Alternatively, filter 30 can be front loaded into catheter C byintroducing floppy tip 35 b into the proximal end of catheter C andpushing elongate member 35 distally. Stop 32 will push against distalsliding element 38 and cause distal loop 34, filter 30, tether 36 a, andproximal sliding element 36 to enter into catheter C and advancedistally through catheter C. In this alternative, catheter C can beadvanced to a region of interest with the filter contained within. Morepreferably, a guidewire can be advanced to a region of interest,catheter C advanced to the region of interest over the guidewire, theguidewire withdrawn from catheter C, and filter 30 front loaded to theregion of interest and deployed as described above.

To recover the filter, catheter C is advanced over elongate supportmember 35 and the elongate support member is withdrawn into catheter C.Stop 32 will abut proximal slider 36, and slider 36 coupled to tether 36a coupled to filter 30 by way of point 36 b will cause filter 30 to berecovered into catheter C by continued proximal motion of elongatesupport member 35 relative to catheter C. Support member 35 preferablyshould be withdrawn sufficiently to at least close the opening of filter30; alternatively all or part of filter 30 and distal loop 34 may bewithdrawn into catheter C. It is preferable to draw the distal loop atleast partially into catheter C so as to reduce or eliminate contact ofdistal loop with the vessel wall. At this time, the filter/cathetercombination can be withdrawn from the patient.

FIG. 4 illustrates an alternative embodiment of a filter of thisinvention in which windsock-shaped filter 40 is attached to elongatesupport member 45 via distal sliding element 48. At the proximal end ofthe filter, proximal sliding element 46 is slidably disposed about theelongate support member and attached via tether 46 a to point 46 b onthe filter. Point 46 b can be constructed in a manner similar to thatfor sliders 46, 48, or can be a structure such as a tube into whichtether 46 a and filter 30 are inserted and held together by crimping thetube, joining with adhesive, welding, or the like. Stops 42 a and 42 bare provided on the elongate support member in order to limit therelative motion of the filter along the support member. Stop 42 a isshown proximal to the filter opening and stop 42 b is shown within thefilter. Alternatively one stop, such as a wire coil or a hypotube,polymer or metal, solid or cut to improve its flexibility, can take theplace of stops 42 a and 42 b. Support member 45 terminates distally atfloppy tip 45 b. Distal loop 47 is affixed to distal sliding element 48.The distal loop serves to keep the filter open during movement of theelongate support member relative to the filter and to prevent theelongate support member 45 from moving radially and collapsing filter30. This is accomplished by keeping the elongate support member, whichslides through the distal sliding element 48, opposed to a vessel wall.A further advantage of distal loop stabilization of wire position isthat the distal loop does not impede entry of embolic particles into thefilter, unlike prior art approaches where struts and the like are oftenplaced proximal to the filter. Another advantage of a distal loop filteris that the mass of the loop and the comparatively large mass of theproximal filter do not overlap during collapse of these structures intoa delivery catheter, and as a result the profile of a delivery catheterfor the filter can be made smaller. Filter 40 can comprise metal orpolymer braid, polymer film with holes drilled therethrough, foams,other filter media as is known in the art, or any of the filter meshstructures disclosed in the U.S. patent applications filed on the samedate as the present application and entitled “Embolic Filters WithControlled Pore Size” (Atty Docket: EV31001 US) and “Embolic FiltersHaving Multiple Layers and Controlled Pore Size” (Atty Docket: EV31002US), the contents of each of which are hereby incorporated byreference herein.

No Loop Filters

FIG. 5 illustrates a distal protection system similar to that shown inFIG. 4, but without the distal loop. Windsock-shaped filter 50 isattached to elongate support member 55 via distal sliding element 58. Atthe proximal end of the filter, proximal sliding element 56 is slidablydisposed about the elongate support member and attached via tether 56 ato point 56 b on the filter. Stop 52 is provided on the elongate supportmember between the distal and proximal elements. The stop limits therelative motion of the filter along the support member. Support member55 terminates distally at floppy tip 55 b which may comprise a coil tipor any of the embodiments described earlier. Filter 50 is comprised ofany of the filter mesh structures disclosed herein. An advantage of afilter with no distal loop is that the mass of the filter assembly isreduced, and as a result the profile of a delivery catheter for thefilter can be smaller. Further, no loop filters have fewer stiffstructures associated with the distal end of the filter. Theseattributes allow no loop filters to cross tighter lesions and to trackmore easily through tortuous vessels.

FIG. 6 illustrates a variation of the distal embolic protection systemshown in FIG. 5. Filter 60 is disposed about elongate support member 65via distal 15 sliding element 68 and is comprised of any of the filtermesh structures disclosed herein. Stop 62 is provided on the supportmember and tether 66 a is attached to the distal end of the stop (atpoint 62 a) and the proximal end of the filter (at point 66 b), althoughthe tether could be attached to either end of the stop or at any pointtherealong. The stop/tether structure limits the relative motion of thefilter along the support member and provides for radial motion of theelongate support member. Support member 65 terminates distally at floppytip 65 b.

Although we have generally used siding elements to describe theinvention, one or more fixed element could take the place of the slidingelements.

While the examples given generally relate to distal embolic protectionfilters it is envisioned that the invention can apply to proximalfilters as well.

While the examples given generally relate to windsock shaped filters itis envisioned that the invention can apply to filters of nearly anyshape including cups, plates, cylinders, ovoids, and others. Generally,the invention is best embodied in filters having an opening facingtowards the direction of flow so that emboli have a tendency to enterthe filter.

The above description and the drawings are provided for the purpose ofdescribing embodiments of the invention and are not intended to limitthe scope of the invention in any way. It will be apparent to thoseskilled in the art that various modifications and variations can be madewithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-20. (canceled)
 21. A device for filtering emboli from blood flowing through a body lumen of a patient, the device comprising: an elongate support member; a filter element attached to the elongate support member, the filter element being expandable from a collapsed configuration when the filter element is restrained to an expanded configuration when the filter element is unrestrained, wherein when the filter element is in the expanded configuration, the filter element defines a cavity having a proximal facing opening, and wherein the filter element comprises a self-expanding filter mesh material; and a self-expanding radial element associated with the filter element, wherein the self-expanding radial element is distal of the filter element, and is configured to maintain the filter element centered in the body lumen.
 22. The device of claim 21, wherein the self-expanding radial element comprises a loop, and wherein the loop is generally circular in shape.
 23. The device of claim 22, wherein the self-expanding radial element has only one loop.
 24. The device of claim 22, wherein the self-expanding radial element comprises two or more loops.
 25. The device of claim 21, wherein the filter element has proximal and distal portions and a central portion, the filter element being attached to the elongate support member at the distal portion of the filter element.
 26. The device of claim 21, wherein the filter element has proximal and distal portions and a central portion, the filter element being attached to the elongate support member at the proximal portion of the filter element.
 27. The device of claim 26, wherein the filter element has proximal and distal portions and a central portion, the elongate support member being attached to the filter element at the proximal portion of the filter element by a single flexible tether.
 28. The device of claim 21, wherein the filter element is attached to the elongate support member by a sliding element.
 29. The device of claim 21, wherein the filter element is attached to the elongate support member by a fixed element.
 30. The device of claim 21, wherein the self-expanding radial element is adapted to not significantly impede the flow of blood through the lumen.
 31. The device of claim 21, wherein the device does not comprise any other self-expanding elements other than the self-expanding filter mesh material and the self-expanding radial element.
 32. The device of claim 21, wherein the self-expanding radial element is made of a nickel titanium wire.
 33. The device of claim 21, wherein when the self-expanding radial element is in its expanded configuration, the self-expanding radial element generally defines a plane substantially perpendicular to the elongate support member.
 34. The device of claim 21, wherein self-expanding filter mesh material defines pores, and when the filter element is in the expanded configuration, an average pore size is from 30 to 300 microns and the standard deviation of the pore size is less than 20 percent of the average pore size.
 35. The device of claim 21, wherein when the filter element is in the expanded configuration, the filter element has a percent open area greater than 50 percent.
 36. The device of claim 21, wherein the self-expanding filter mesh material has a tensile strength greater than 70,000 psi.
 37. The device of claim 21, wherein the self-expanding filter mesh material is made of metal.
 38. The device of claim 21, wherein the self-expanding element attached to the elongate support member.
 38. A device comprising: an elongate support member; a filter element attached to the elongate support member, the filter element being expandable from a collapsed configuration to an expanded configuration, wherein when the filter element is in the expanded configuration, the filter element defines a cavity having a proximal facing opening, and wherein the filter element comprises a self-expanding filter mesh material; and a self-expanding radial element attached to the elongate support member and configured to collapse into a catheter, wherein the self-expanding radial element is distal of the filter element, and is configured to maintain the filter element centered in a body lumen of a patient.
 39. The device of claim 38, further comprising a sliding element that slidably attaches the filter element to the elongate member, wherein the self-expanding radial element is attached to the elongate support member via the sliding element.
 40. The device of claim 38, wherein the self-expanding element comprises a hinge.
 41. The device of claim 38, wherein the self-expanding element comprises a zone of preferential bending.
 42. A method comprising: introducing a catheter in which a device is at least partially positioned into a body lumen of a patient, the device comprising: an elongate support member; a filter element attached to the elongate support member, the filter element being expandable from a collapsed configuration when restrained within the catheter to an expanded configuration when unrestrained, wherein when the filter element is in the expanded configuration, the filter element defines a cavity having a proximal facing opening, and wherein the filter element comprises a self-expanding filter mesh material; and a self-expanding radial element associated with the filter element, wherein the self-expanding radial element is distal of the filter element; positioning the filter element distal to a treatment site; deploying the filter element from the catheter and into the body lumen of the patient by at least withdrawing the catheter proximally, wherein after deploying the filter element from the catheter, the self-expanding element engages with a wall of the body lumen to maintain the filter element centered in the lumen defined by the vessel.
 43. The method of claim 42, wherein the device further comprises a sliding element that slidably attaches the filter element and the self-expanding radial element to the elongate support member, and a stop attached to the elongated member proximal to the sliding element, wherein as the catheter is withdrawn proximally, the filter element remains inside the catheter until the distal sliding element contacts the stop.
 44. The method of clam 42, further comprising inserting a proximal end of the elongate member into a distal end of the catheter. 